The present invention relates to an improved fluid handling device for providing a more efficient fluid flow. In particular, the present invention relates to an improved vaneless impeller for such devices, which impeller relies on the generation of frictional and rotational forces to propel or convey the fluid efficiently and to produce a desired pressure differential. The impeller may be rotationally driven so as to produce an accelerated fluid flow in a radially outward direction, in which case the device functions in the manner of a fluid pump, or the impeller may be non-driven with the fluid flow being directed radially inward, so that the device functions in the manner of turbine.
Centrifugal fluid conveying devices, and in particular, air pumps or blowers, utilizing a vaneless impeller for producing an accelerated radially outward fluid flow between co-rotating disks of the impeller are known in the art and the theoretical considerations of such devices have been extensively analyzed. In this regard, see for example, U.S. Pat. No. 1,061,142 issued May 6, 1913 to N. Tesla and the articles by W. Rice, "An Analytical and Experimental Investigation of Multiple Disk Pumps and Compressors", TRANSACTIONS OF THE ASME--JOURNAL OF ENGINEERING FOR POWER, July 1963, pp. 191-200, and S. H. Hasinger et al, "Investigation of a Shear-Force Pump", TRANSACTIONS OF THE ASME--JOURNAL OF ENGINEERING FOR POWER, July 1963, pp. 201-206. In such devices, the rotor or impeller is driven by a motor and is constructed of a series or plurality of coaxially spaced annular disks. Due to the annulus present in each disk, fluid is drawn in proximate the center of rotation and is subsequently propelled radially outwardly in a spiral path as dictated by the actions of two types of forces. These forces are the frictional forces imparted to the fluid by the side surfaces of the rotating disks and the centrifugal forces resulting from the angular motion of the disks. In all of the known devices of this type, each of the disks is provided with respective side surfaces which are straight and the disks are coaxially mounted so that the side surfaces of all disks are parallel. Consequently, in the known devices, the spacing between the facing side surfaces of adjacent pairs of disks is constant in the radial direction.
Although devices of this type have been known for some time, they have not been extensively used, in a practical sense, due to a low-efficiency. One major cause of the low-efficiency of such devices is the energy loss incurred in the vicinity of the disk annulus which is due to the lack of a smooth transistion from an axially directed fluid flow, i.e., along the axis of rotation of the impeller or rotor, to a radially directed flow between the rotating disks. In order to overcome this problem, it has previously been suggested to incline the straight and parallel disks with respect to the axis of rotation so that they face in the direction of the fluid inlet, or to curve the innermost portions of otherwise straight and parallel radially extending disks in the direction of the fluid inlet.
Although the reduction of the energy losses incurred in the vicinity of the disks provide an improvement in the efficiency of the above-mentioned type of device, i.e., the annular disk impeller or rotor, efforts to further improve or optimize the efficiency of such devices have continued. In this regard, it has been discovered that certain theoretical assumptions concerning the specific nature of the fluid flow dynamics between rotating disks and, additionally, assumptions concerning the corresponding optimum design of such disks do not agree with experimental findings. In particular, experimental test results have strongly indicated that the fluid boundary layers which form on rotating surfaces do not stabilize asymptotically with increasing radius as was heretofore believed, but rather they tend to vary along the entire radial distance. Thus, the straight and parallel disks do not allow for an optimal flow pattern, either in terms of flow output or with regards to efficiency.